1. Field of the Invention
The present invention relates generally to optics and, more specifically, the present invention relates to splitting or combining optical beams.
2. Background Information
The components used in optical networks are often complex structures, individually fabricated for specific applications of use. Though complex overall, many of these components are formed of relatively simple individual optical devices combined to achieve complex functionality. Just as the advent of semiconductor logic gates facilitated the creation of the microprocessor, the development of simple optical devices performing functions such as coupling, splitting and combining allows system designers to form increasingly more complex optical circuits.
Of the various basic optical structures, signal splitting/combining is one of the most important. A single-mode optical waveguide 3-dB Y coupler or power divider is an important component that can be used in switches and modulators of for example the Mach-Zehnder interferometer (MZI) type. A conventional Y coupler is typically formed of a straight input waveguide for receiving an input signal and two output waveguides that meet at the input waveguide. Ideally, where the two output waveguides meet, a sharp vertex or inner edge is formed forming equal branching angles for the two output waveguides so as to equally split the input optical beam into two output optical beams.
In practice, however, known Y couplers often lose a sizeable amount of input energy due to limitations in device fabrication. For instance, fabricated Y couplers typically end up having a blunt vertex instead of a sharp vertex, which introduces radiation loss in the Y coupler. Radiation losses of 2-3 dB are not uncommon in known fabricated Y couplers of conventional design. In addition, an equal power splitting ratio cannot always be well controlled in conventional Y coupler designs. As can be appreciated, equal 50%—50% power splitting of a Y coupler is desired for the high extinction ratio for optical uses such as modulator and switch applications.